System and method for storing and transferring a cryogenic liquid

Abstract

This fluid storage and transfer system includes a first storage tank and second storage tank configured to contain cryogenic liquids. The first storage tank has a heat exchanger. A second cryogenic liquid from the second storage tank subcools a first cryogenic liquid in the first storage tank and pressurizes the first storage tank. The first storage tank is then further pressurized using the heat exchanger. The first cryogenic fluid is transferred from the first storage tank to an end point. In an example, the first cryogenic fluid is liquefied natural gas and the second cryogenic fluid is liquid nitrogen.

What is claimed is: 
     
         1 . A system comprising:
 a first storage tank configured to contain a first cryogenic liquid, wherein the first storage tank is insulated;   a second storage tank configured to contain a second cryogenic liquid, wherein the second storage tank is connected to the first storage tank to provide a flow of the second cryogenic liquid that subcools the first cryogenic liquid and pressurizes the first storage tank;   a heat exchanger connected to the first storage tank, wherein the heat exchanger is configured such that the first cryogenic liquid flows into the heat exchanger, vaporizes, and flows into ullage space in the first storage tank; and   a piping system connecting the first storage tank to an end point.   
     
     
         2 . The system of  claim 1 , wherein the first cryogenic liquid comprises liquefied natural gas and the second cryogenic liquid comprises liquid nitrogen. 
     
     
         3 . The system of  claim 1 , wherein the second storage tank is configured to be removable from the first storage tank. 
     
     
         4 . The system of  claim 1 , wherein the second storage tank is connected to a bottom of the first storage tank. 
     
     
         5 . The system of  claim 1 , wherein the second storage tank is connected to the first storage tank such that the flow of the second cryogenic liquid is into the first cryogenic liquid. 
     
     
         6 . The system of  claim 1 , wherein the heat exchanger is configured to use at least one of gravity or head pressure to enable flow of the first cryogenic liquid through the heat exchanger. 
     
     
         7 . The system of  claim 1 , wherein the piping system is connected to a bottom of the first storage tank. 
     
     
         8 . A method comprising:
 transferring a second cryogenic liquid from a second storage tank to a first storage tank that is at a first pressure, wherein the first storage tank contains a first cryogenic liquid different from the second cryogenic liquid, wherein the first cryogenic liquid has a boiling point less than or equal to −150° F. under normal atmospheric pressure, and wherein the second cryogenic liquid has a boiling point below that of the first cryogenic liquid;   subcooling the first cryogenic liquid in the first storage tank with the second cryogenic liquid;   pressurizing the first storage tank with the second cryogenic liquid to a second pressure greater than the first pressure;   pressurizing the first storage tank with a heat exchanger to a third pressure greater than the second pressure; and   transferring the first cryogenic fluid from the first storage tank when the first storage tank is at the third pressure.   
     
     
         9 . The method of  claim 8 , wherein the first cryogenic liquid comprises liquefied natural gas and the second cryogenic liquid comprises liquid nitrogen. 
     
     
         10 . The method of  claim 8 , further comprising venting the first storage tank after the transferring. 
     
     
         11 . The method of  claim 8 , further comprising filling the first storage tank with a cryogenic liquid after the transferring. 
     
     
         12 . The method of  claim 8 , further comprising using at least one of gravity or head pressure to enable the first cryogenic liquid to flow through the heat exchanger. 
     
     
         13 . The method of  claim 8 , wherein the pressurizing the first storage tank with the heat exchanger continues during the transferring of the first cryogenic fluid from the first storage tank.